Facebook Marketplace is the best place to find used Smarts. Everything is available on there. The 451 (2008-2015) is a fun little car, but the automatic transmission takes some getting used to. It's an auto with an electronically actuated clutch, and sometimes you find yourself head banging when it switches gears unexpectedly. Adds to the fun, imo.
The 453 (2016+) has a DCT automatic. Depending on your budget you probably want a 2016+ Passion Cabrio. They can come pretty loaded with heated leather seats, cruise control, auto lights and rain sensing wipers, etc. The options vary wildly.
@NascarJohnny They're definitely fun, versatile little cars. But yeah they're not super powerful. If you're looking for a quicker micro hatchback, the Fiat 500 Abarth may suit you as well. Hard to find in automatic (which I assume if you're just looking for an around-town car), but they exist. Also available in cabrio form factor.
@NascarJohnny - Fair enough. The smart is a great car. We missed ours so much after we turned in our lease that we recently bought another. You just can't stop smiling and appreciating the car when you're driving, and I've driven all levels of cars... used to have several higher end Mercedes and a Nissan GTR as well. The Smart is among my favorite driving experiences.